Problem:
That dang touchpad is screwing you up by being so sensitive that when you brush it w/your thumbs while typing, it resets the cursor position to some other god-forsaken place in your Word document and screws up your paragraph.
Solution A:
C: > Program Files > Sony > Setting Utility Series > VCCPointingDevice > Uncheck the box next to "Enable"
*Create a shortcut to this program so you don't have to go through all the hassle of finding it again when you want to re-enable your touchpad.
Solution B: for when your "VCCPointingDevice.exe" is not there (like my Z-690's wasn't)
Start > Control Panel > VAIO Control Center > (on the left) Keyboard and Mouse > Pointing Device > Uncheck "Enable" > Apply
*Leave this open until you're ready to re-enable your touchpad (if you're planning to do it soon before you restart/log off/shut down). It's just easier than finding it again.
*Crate a shortcut for "VAIO Control Center" on your desktop if you plan to do this often.
Solution C: because Sony can't make up their god dang minds about where to put stuff...
Start > Control Panel > Sony Notebook Setup > Device > uncheck 'pointing device'
